Posted
by
Hemoson Friday January 05, 2001 @11:14AM
from the intergalatic-planetary dept.

jdoire writes: "Using a thin metallic film of americium-242m, a rocket could reach Mars in only 2 weeks. This is made possible because the nuclear material could be used both as a source of energy and as a propellent material, making the engine very efficient and light weigth. Check ScienceDaily for the full story."

The article is slashdotted, but from the Slashdot description, it sounds like we're talking about a radioactive substance that would be expelled for a reaction force. Is that right? If so, then it sounds like you don't want to be anywhere near or downwind of the smoke cloud this thing makes when it takes off.

I hope I'm misinterpreting this, because my first reaction is: "Gee, that's stupid." I mean, it doesn't sound as bad as Orion, but still...

The properly attributed text is thus:LISTER: What do you believe in, then? Do you believe in God?
RIMMER: God? Certainly not! What a preposterous thought! I believe in
aliens, Lister.
LISTER: Oh, right, fine. Something sensible at last.
RIMMER: Aliens, Lister, with technology so far in advance of our own we
can't even begin to imagine.
LISTER: Well, that's not difficult. Mankind hasn't even got the
technology to create a toupee that doesn't get big laughs.

...and I know for a fact that both Project Helios and Project Orion were not intended for use inside the atmosphere of Earth.

Some early incarnations of Orion actually did call for launch inside Earth's atmosphere. At the time it seemed (and still seems) the cheapest way to develop "very heavy launch" capability quickly. While there is still a fallout issue, one can envision scenarios where people would trade fallout for unpleasant consequences--e.g., to get equipment into space in order to prevent Earth's colliding with a large meteor.

Small half-life means highly radioactive. That's why you can hold a piece of uranium-238 in your hand (half life 4 billion years), but I would not recommend holding a piece of say Cobalt-60 (halflife 5 years).

Yes, the length of an efficient Hohmann orbit is a lot greater than the straight line distance to Mars. But with a travel time of two weeks, efficiency goes completely out the window; you would be practically taking a straight line path.

Calculating the actual orbit is a non-trivial task, but I recall that for the outer planets, at least, the straight line approximation mghiggins did wouldn't be very far off (in terms of relating travel time and acceleration) for a constant-thrust ship of even.1 G.

Also, I'd assume "trip to Mars in 2 weeks" means when Earth is passing closest to Mars in it's orbit, so the.15 G figure is probably more accurate, and even a wide margin of error wouldn't change the answer to the "would I be pureed by this acceleration?" question.

heh... yep... See what happens kiddies, when you don't have your regular intake of sugar and caffeine. You miss all kinds of things. The above figure of 16000 km./hr. should be 16000 km./min. The actual figure for hourly travel is now 960,000 km./hr.

I see that you have been reading Zubrin, he a very convincing man, I heard him speak at a Mars Society talk here on campus. Unfortunately there are several problems with just packing up and heading off to mar right now.

As one of the other replys mentioned, it takes time to build spacecraft, especially one that is supposed to make a 9 month journey. And right now it would actually take longer than that because we are not in the proper alignment with mars for the shortest possible trip.

It also takes money, and right now the government of the United States has this policy of supporting only ONE big science project. I am helping out with research in High Energy Physics, and everyone knows in that field knows that the ISS was choosen over another particle accelerator. Those were the two choices at the time.

The level of technology is not suffecient.

Currently the only reliable engines that we have are chemical fuel rockets. All of the other ideas out there whether it be plasma, solar sails, Hall-effect engines, etc... are either not ready, not properly tested, or have major problems that need to be sorted out. Plasma is one of the better ideas and it is years away. Solar sails have an interesting problem with a harmonic ripple effect on the edge of the sail which doesn't damp out in space and causes the sail to collapse. Most of the other engines would take extremely long amounts of time, like the Hall-effect. Although this nuclear engine sounds really nice, I seriously doubt that it has been properly tested.

Also we really don't have a good way of protecting the travelers from the large amounts really nasty radiation that they will have to deal with. Not only will they have to worry about the radiation while enroute, but also while on the planet. Mars does not have a magnetosphere like Earth does, nor does it have a suffeciently thick atmosphere. Both of those things are why we don't have to worry too much about solar flares completely fscking us up. Currently the best way we have to deal with radiation is lead. It will be a real pain to get enough lead up into space to protect the astronouts. Frankly the last thing we need to have is our heros coming home completelyl sterile and then dieing of cancer shortly after returning.

Living quarters are still being tested for the Mars direct plan. They have their tunafish can living quarters in Canada right now. They are always looking for help in testing it.

As mentioned before we are not in position for shortest travel time to Mars. I forgot the exact number but it is either 12 or 20 years from now. If I remember correctly almost all of the figures that are given for enroute times are calculated assuming that the Earth and Mars are in proper alignment so as to give the shortest possible time.

I want to see us go to Mars, but I don't want us to rush it. I am sure that you have taken note to the backlash that NASA took when it lost several probes in a row. Those were unmanned and they got reamed big time. Imagine what the public would do if NASA lost six astronouts while enroute to or on Mars. Chances are good that NASA would either get axed or be so horribly crippled from budget cuts that it might as well be dead. Although the technology we have currently is capable of sending manned missions to Mars, we need to do more research and more testing and patience before we can achieve a SAFE mission to Mars. I am sure we will get there, and within my lifetime. Why, because it is one of NASA's priorities. Right now they are spending most of their budget on the ISS, as you know, which IS necessary. I personally believe that having a working space station is as necessary as sending someone to another planet. Once they are done with the ISS then they can move onto providing more time and funding to the Mars project.

Interesting point (speed = 0.014 x c). Time & mass dialation could be measureable, but it's still not enough for serious issues to occur. The wierd/cool stuff doesn't appreciably happen (IIRC) until about 90% of c.

Mars Direct isn't nearly as ephemeral a plan as the Apollo missions were (the Apollo missions didn't leave automated fuel production facilities and human habitats on the moon, for instance) but I expect the end result would be the same: a half dozen missions, followed by nothing.

If you want to see real exploration of space, the way to do it isn't to throw a few men to Mars, damn the cost; the way to do it is to reduce the cost!

That reminds me of the time that an overzealous newspaper editor in Washington (I can't recall which of the papers it was) blindly changed the text of a business report to read that the market was expected to soon be "in the African-American".

Oops, you meant when the unit is escaping the Earth's atmosphere, duh.

I think they would used standard solid fuel boosters to get the 2nd and 3rd stages (also solid fuel propellant) into space and after the payload has made it out of "range" (?) of our atmosphere the 'high-speed' engines would kick in.

Getting americium isn't that impossible, but it is dificult. The steel and metals industry uses americium to gauge the thickness of metals.

In fact the company I work for now probably has a few pellets from many years ago. I don't think they are of this isotope, but still, it can be found.

Oh, BTW, if it wasn't mentioned, the half life of Americium-242 is about 16 hours. It's relatively easy on the environment. However, Am-241 has a half life of 432 years. And to make matters worse, Am-243, the most stable isotope has a half-life of 7300 years.

By the same token, a 1G acceleration will get you halfway in 1.4 days, or all the way in about 3 days

I remember having a handy-dandy graph for different amounts of multi-G acceleration from "The Ringworld RPG" [btinternet.co.uk] that really gets you thinking about how fast constant 1G (or 40G!) really is.

(ahem) "doing the math", one week of 1G constant acceleration will get you 182,891,520,000 km (or about 30 thousand times further than pluto!)
My math may be off (:!) but you get the idea!
(and yes, this may not indclude decerlartion... but still! Anyone who is math-enabled, please have at it!)

running out of air, freezing to death, radiation, every astronaut since Yuri Gagarin was prepared for these potential fates.

It's called being a hero. Knowing you're expendible is one thing. But knowing that it was for a cause as high as space exploration (imo, there are few higher), makes it worthwhile. Remember the proposal a couple of years ago, at a space-science conference, where a scientist said that if a Mars trip were one-way for the astronaut, it would make the whole project cost about 1/3, and who would volunteer for such a mission - go to Mars, but certain death? Every person in the audience raised their hand.

Assuming the 2-week estimate is based on the minimum distance this means that it would take 336 hours to travel the 54,500,000 km for an average speed of about 45,000 m/s. If the acceleration of the ship could be held constant at 10 m/s^2 this means that a near Earth gravity effect could be achieved for about 75 minutes at the begining and the end of the trip. A near Mars gravity effect (3.7 m/s^2) could be maintained for over 3 hours on each end of the trip.
In order to maintain an Earth like gravity for the entire trip the ship would need to attain the speed of 740,000 m/s (accelerate at 10 m/s^2 half way out and then flip the ship around and decelerate at 10 m/s^2 the rest of the way). In order to maintain a Mars like gravity for the entire trip the ship would need to attain the speed of 450,000 m/s (accelerate at 3.7 m/s^2 half way out and then flip the ship around and decelerate at 3.7 m/s^2 the rest of the way).
Of course either 450,000 m/s or 740,000 m/s would give us measurable time/space/mass dilation problems. So you gain a little weight you get a little smaller and you age a littler slower -- basicly you would be young, short, heavy and hauling ass!!!

I hate to admit it, but it looks like this is one dirty idea. They plan to use fision products as propellent! That is nasty, much worse than NERVA, even Orion. If they manage this it might be to dirty to use in the air.

What really bothers me is the number of groups that think that we shouldn't be putting our radioactive contaminants and materials into space... There's a heck of a lot more out there to worry about - just look at what's happening to Galileo everytime it flies around IO...

But yeah - liftoff issues are a bit of a bother - that's why we should have nuclear fuel production in space - preferably somewhere handy but not too close to the Earth. Use conventional rockets to ferry people to the moon base, mine, and refine the fuel there. Nuclear fuel appears to be the way to do it now - might as well try to do it right. But then again, we'd need quite the infrastructure to get us there, and that doesn't seem to be happening soon.

And no, nuclear explosions will not hurl the lunar base at interstellar speeds out of the solar system to go on a series of adventures.

I've read the article, and I've read all the comments, and I still haven't seen anyone guess a feasible design for a reactor/propulsion system using this stuff. Surely there's some nuclear physicists with the back of an envelope handy who'd care to enlighten me?:-)

It wouldn't be used in the atmosphere, or withing the direct gravitational pull of the earth. It wouldn't even work. They would have to boost the thing into orbit with a conventional rocket first.

Just like with the ion propelled rocket, the power doesn't lie in immensely high thrust but in the ability to sustain the thrust over the space of weeks or months, instead of short bursts of no more than a few minutes.

The nuclear engine would continue accellerating the vehicle slowly but steadily for weeks, accellerating it to a velocity far higher than a conventional engine, which requires you to drag a fuel tanks the size of a house along, which will be used up in a matter of minutes.

So don't worry about a nuclear rocket leaving a great radioactive mushroom cloud in it's tail.

I agree, to a point. But here's the reality: We aren't there yet. If we started building right this minute, we'd be there in about five years. You're not going to see routine trips to Mars for 10 years at least.

Secondly, the ISS may be the biggest boon to interplanetary space travel we've come up with so far. With it, we have the possibility of starting from outside the gravity well, which is the biggest fuel burn we have with any space travel.

Finally, if you don't like what NASA is doing, why not do it yourself? Seriously, private sector space travel is getting more likely and more lucrative by the day. Go get some funding, and do it yourself!

What good is it to have tiny nukes if we have no ability to deliver them to other planets, where hostile alien races are sure to be setting up a similar attack on us? We must strike first to establish humanity's supremacy in the galaxy, and a super-fast spaceship with horrifyingly destructive weapons is the first step.

I don't know if this is an urban legend or not, but I had heard that petroleum is actually more valuable as a lubricant than as a fuel, because we can't yet create synthetic lubricants which are as good as the real thing. The danger is that all of our machines may literally grind to a halt when we run out of oil, even if the machines themselves are solar/nuclear/etc powered.

That last page produces the real gem: this patent [godunov.com] is for a "Magnetic recording medium comprising a solid lubrication layer of fullerene carbon having an alkyl or allyl chain". The abstract reads:

A magnetic disk has a magnetic medium or a protection film, and a solid lubrication film formed on the medium or the protection film and consisting of a fullerene C60, C 70 or C84 and an alkyl or allyl-chained fullerene. The lubrication film provides the disk with high mechanical durability and high linear recording density.

A fully fluorinated buckyball would create the
slickest molecular lubricant known to man, C60F60. The uses for a molecular
lubricant are boundless, limited only by our imagination.

Of course, I don't know that anyone's actually assembled such a molecule. I located an article called Just Rolling Along [199.203.151.110] which discusses tungsten disulfide, which is similar to buckyballs. It is, however, expensive to produce, and difficult to make in quantity; This is what we're waiting for. Incidentally, I did find one article that gave hope for this, under the heading "Cheap Buckyballs [lucifer.com]". Amusingly enough (to me) the anchor tag is named "cheapballs". I guess when you're hopped up on this much sugar all kinds of things are funny. If anyone has access to the text of "Journal of Organic Chemistry, March 8" perhaps they could help out here.

So in summary, there ARE better lubricants than those cracked from crude. They are not, however, currently on the market, as they are expensive and time-consuming to produce. However, science marches on, and we'll solve this problem, too.

I believe Ford strapped a small scale nuclear reactor onto a car in the '50's or '60's. I rememberr seeing something like that in popular science a while back. Can't seem to find a link though. The main reason we've never seen this become mainstream is the danger involved. It's bad enough when Joe Sixpack can get behind the wheel of his SUV and cause an accident that kills 4 or 5 people, but what if he wrecked his nuclear car. We'd be dealing with a China Syndrome type of disaster instead of a small explosion.

If something went wrong on a MOON mission, we would ahve left our astronauts out there to die

True, but only if there were no other solution. Remember Apollo 13 (the mission, not the very good and ultimately enjoyable movie)? NASA and friends did everything in their power to bring the boys home -- when it would have been much less expensive to just turn the radios off, send all the engineers home, and tell the media that they lost contact with the astronauts.

Nuclear power is evil, regardless of benefit.
Coal fired power is evil, regardless of benefit.
Oil fired power is evil, regardless of benefit.
Natural gas power plants emit pollutants and so are evil too, regardless of benefit.
Geothermal and solar... hmmm... don't seem to work like greenpeace says.

So for the last ***10 YEARS***, not one new power plant was build in CA nor any expansion of existing plants.

Waaaaah! We have an enegry shortage in CA due to... uh.... yeah!.... DEREGULATION! Surely strict environmental laws are not to blame. And repealing then would be a right wind radical thing to do.

Let's lobby the DOE to force other states on the grid to sell us power at a mandated discount. They want to suck off the grid and pollute other states so they can have blue skies?!

Well, hey, CA, you download off the grid, you have to upload too. CA is no different than a w4r3z l33ch. If you want power, you have to get dirty... you have to pay for it just like everyone else.

Sure I agree in theory that we need a cheap way to get off earth before we need a cheap interplanitory travel. However it turns out not to be stricktly true.

Assume getting off earth is expensive, but a break through tommorow turns up with cheap travel between solar systems. That means that the space station can send probes to do fly-bys of distant planets, and 20 years latter have the satilight return for repairs before going to a diffent solar system. (Of course that would be fairly close). reusable probes would be a break through, and while they are still expensive they would be a lot cheaper then starting with a new probe, and would give us data we cannot get today. (We cannot do a fly-by of other solar systems with current probes, but this might give is the ability to do fly-bys of farther out systems)

Second, and more likely is that eventially we get a fairly cheap way to get off earth. We don't want to start at ground zero devolping cheap interplanitory travel. A lot of early work in research is better done by small teams, once the theory(s) are devolped you then take a large team to impliment it. So once we have a cheap way to get off earth we really want to quickly get a cheap way to get elsewhere. Getting off earth might end up taking 3 hours, who cares, but if that super cheap drive that takes 3 hours to get off earth can't reach faster speeds it is wrothless for getting to mars. Take that cheap but slow drive as a farry trip to space, and switch to a ship with cheap interplanitory drive, and you can then reach mars in 2 weeks. Nobody would allow a ship with radio active by-products like the above in the earths atmosphere, but it si harmless in space, so we combine them.

interesting. It's not currently "on", though it was last year. There has been "talk" for years about a refit, knocking down the three big ugly smokestacks. (it's estimated that tens of millions in tourism could be gained if these smokestacks were removed - it's not a mere case of NIMBY, because there's a nuke plant less then 20 miles away).

How does it go? "Never attribute to malice what can be attributed to stupidity"?

There was a project at a university supported by the automotive industry to develop a nuclear-powered car, but then there was this little problem at Three Mile Island and the funding pretty much disappeared. Add to that two things: (1) The researchers had made little progress to the auto makers goal, though they did a lot of research that is important for other things (materials research); (2) There has been a propaganda machine (mainly by the US Gov, I guess) to scare the sense out of people wrt radiation - our "nuclear deterrent" is more effective when people are afraid of it.

You can find out about the automotive research by looking for something like "nuclear-powered car" on Google. (Sorry, don't remember the name of the project off-hand.)

IEEE Spectrum had a good series about Three Mile Island some time ago; but I don't have the issue numbers.

Physics Today, Physics News, or Science had an article in the past year (or 2) about the dangers (real and imagined) of radiation et al.

Last Note:
Present day nuclear reactors use fission; fusion is still a pipe dream; Cassini (and many other space probes) used RTG's (RadioThermal Generators) which rely on natural decay processes; a nuclear bomb is a very complicated machine - a fission reactor in a car (which is probably unnecessary, see RTG's) might 'meltdown' or leak radiation, but it wouldn't become a bomb. The worst-case scenario is probably (and this is just a guess) that the car could explode just as it could with conventional fuel (and how likely is that? *shrug*) and then there would be some nasty clean up to do _if_ the design is so poor as to not contain the fissionable materials. Keeping the reactor safe from an external explosion is 'easy' - we know how to do it. Making a cheap, low-maintenance, and self-containing reactor is probably the hard part; but mostly because of the first two parts.:-)

Funny, I remember reading (out of grim curiosity) an article several years ago from the Chronical with the headline "Russian Satalites Leaking Radiation", or something to that effect. The entire article was about how there are several former Soviet nuclear satalites in relatively high orbits that had minor breaches in the power supply and were leaking radiation into space, and how that was really bad. It is scary how ignorant of radiation people really are.

I think that the prime example of stupid radiation protests has to be the banning of the process of irradiating eggs. Before that ban there was very little worry about getting salmonella (sp?) poisoning from eating raw eggs, now I have to coddle the eggs every time. Ignorance makes it possible.

Now, call me crazy, but people keep assuming that an in-atmosphere launch is a given when dealing with spacecraft. I doubt very much that this drive is intended for use in an atmosphere, and I know for a fact that both Project Helios and Project Orion were not intended for use inside the atmosphere of Earth.

But, since you mentioned them, I just want to comment on Projects Orion and Helios, related to this article by the fact they too were potentially great boons to space travel way back twenty years ago:
Having become aware of the projects way back in the eighties because of a children's book(!) I began to research as much as I could on the projects. I really began to gather information when I got connected to the internet back in 1996. The internet is a wealth of information but in this case 98% of what you'll find will be either pure dross or pure fiction dressed up in science sounding terms. I'll add "in my opinion" rather than just state the above as a fact - IANASY (I Am Not A Scientist Yet). I've let my search lapse in the last few years mainly because of all the extra fake and useless info that appeared on the internet after films like "Deep Impact" which briefly mention Orion or Helios. But from what I gathered, the official reasons the projects were terminated rather abruptly were highly unlikely, the main one cited being the SALT (Strategic Arms Limitation Treaty) and SALT-II treaties with the Soviet Union. A second reason often given was that the '...radiation problem caused...[by the detonation of nuclear devices]...an unavoidable health risk[to the crew].."

Looking over the technical details I managed to track down, I do not believe this reason. Even with limited knowledge, most people would be able to proffer ways of protecting a crew from any major health risk - working only on a design basis. Fears of contaminating the Earth's atmosphere seem unjustified considering it would be possible to limit operation of either the Orion or Helios drive(for want of a better term) to an acceptable distance from Earth. I don't mean to spread paranoia, but at the very least the people who cancelled these projects were misguided - I leave any other alternatives up to your imagination!

I'm not an amoral person who puts science before people : NATO's use of DU(Depleted Uranium) based weapons is deplorable; fission is an unsafe and unnecessary technology for use in power stations; the use of growth hormones in livestock farming and relatively untested GM techniques in Agriculture is plain crazy in Western economies. The fact remains that Orion and Helios were two projects which shouldn't have been cancelled.
I hope to goodness that, just because this new drive employs a radioactive isotope, it isn't designated 'too risky' out of hand - which seems to be a popular thing to do nowadays. (By the way, I know it's a different isotope, but check your smoke alarms....there's a good chance it contains Americium 241 (probably about 0.9 micro curie)

(By-the-by, if you're planning to look for info on Orion or Helios, try the following phrases "Advanced Propulsion Design", "JPL", "Helios" and "Orion" You'll also find that various university professors have, at one time or another, written papers on the subject - try contacting your local university's physics department. )

All of your complaints are easily explained. The slashdot editors are illiterate. Either that or they've been replaced by the equivalent of a procmail filter that rejects 99.99% of all stories and blindly posts the remaining 0.01%.

Think about it, it would work. For any apple story insert some lame comment about jobs from a fortune database. For linux stories some comment like "I'm glad to see that linux is finally immanitizing the eschelon".

Gack! I've figured out to much. The VA linux corporate assassins just knocked down my door and are in my office.

Fortunately since the collapse of their stock they couldn't afford competent assassins, nor weapons beyond a broken nerf gun purchased at a garage sale for a nickel.

But Greenpeace do more than just cause trouble, but then you knew that, right? I recycle, that is a lot more helpful than cleaning up litter. But there is a limit to what one person can do, that's why demonstrations and lobbying are required, to point out to those with the power to effect large scale changes see that it is wanted. As it happens I agree with the idea of nuclear power - when done properly, it's a great deal cleaner than power from fossil fuel generators and far more sustainable. My objection is that safety and cleanliness are compromised by greed and laziness. I'm not a whiner, I do what I can, but I'm only one person and I have a very small amount of money compared to the power companies, and they are the ones that need to change, just as much as the general public does. No change is effected by just sitting there and doing nothing, the foundation of your country being an excellent example of this.

Actually, I said measurable not significant. You are right that the dilation factor would be quite small. In fact the dilation factor would be between 1.00000112500189844105957732041824 and 1.0000030422361049666869703351748 for speeds between 450,000 m/s and 740,000 m/s. However, over the course of 2 weeks this dilation factor for time would mean that the a "stationary" (quotes intentional) object would experience 1209600 and the space ship would experience between 1209596 and 1209599 seconds.

OK, so you're not that much younger than your twin brother, but you are by as much as 4 seconds.:>

The economics of the issue dictate that we need to have a way to cut down the travel time from years to months.

If we have an affordable way to travel in months to the nearby planets, then the solar system and the stars are open to us.

the model is that of the Polynesians as they spread over the Pacific ocean. There plenty of small objects beyond Pluto that could act as stepping stones. never mind things like the asteroid belt. Earth crossing asteroids could suddenly become viable economic entities for carrying things between the inner and outer solar system

There are many problems of supply that would have to be worked out. But we could certainly build a network over time, terraform an asteroid or two, mine a comet for water. the challenges are formidable, but not out of the question.

Probably it could power an automobile for awhile, but that's not the only consideration we have to take into account. How come we don't just mount a nuclear reactor inside all new cars? A load of fuel could probably keep the thing going for years...

Anyway, I never could see why people get so worried about us using up all of our oil. It's all simple economics: right now, it doesn't make sense to look for a new fuel source. We have plenty of oil, and it's not doing any good where it is. When it becomes too expensive to obtain, we'll find another energy source real fast.

Mini nukes? Hell NO. We need full-out neutron bombs to decimate an entire planet's population and sterilize it properly. I say we use the americium for space travel and everything else to scorch the surface and inialate alien species.

2001-01-04 22:49:49 New Nuclear Spacecraft: Travel To Mars In Two Week (articles,science) (rejected)

Maybe each editor should be required to give his name when rejecting a story, so as to take responsibility. He might even give a short reason for the rejection--just like moderators have to give a short reason for their scoring.

First saw the idea of using direct fission products for propolsion in an SF story published in the '40s, I read it in the '60s. Gas core nuclear rockets based on u235 hexafloride were studied in the '50s, 60s, and '70s. Uranium saltwater rockets get the same performance but are a lot easier to build. Looks like the first u235 saltwater reactor was build during the manhatten project and I believe the use of such for rocket propulsion was patented (secret patent) at that time.

It does look like using americium would simplify things... But, since large scale americium production appears to require the use of breeder reactors it is a political dead end in the US right now.

Your calculations would be great if you were flying from point A to point B in a straight line, but unfortunatately it's not that simple.

Firstly, you're moving about in Sol's gravity well, so you can't just point at Mars and pull the trigger. Instead, what you want to do is move into a higher (faster) orbit around the sun.

Secondly, Mars moves!:) So not only do you have to worry about the eccentrities of getting into a Solar orbit at Mars' distance, but you have to time the process such that Mars will be there when you arrive. Depending on the positions of Mars when you leave terrestial orbit, this can be non-trivial.

I Am Not An Orbital Mechanic, and perhaps someone who is could do the real math, but I think that the distance covered is far greater than you've assumed.

However, it seems to me that the accelerations involved are still not extreme. I may be wrong, but I think that a 1G acceleration gets you to Mars in ~ 2 weeks, taking orbital mechanics into account. 1G is a magic number, as it would simulate the gravity you're experiencing now - good for bone mass retention.:)

Well, if we just count manned US Space Shuttle launches, the error rate is only about 1% out of 100 launches. I'm not a gambler but I'd take those odds any day over Amtrak. You might survive the trip but you'll probably get mugged in the parking lot.

The really neat thing about this is that it would allow us to make rescue attempts if something goes wrong. If something went wrong on a MOON mission, we would ahve left our astronauts out there to die. There would have been no way for use to rescue them. The president even had a speech written just in case. Starving to death or slowly running out of air doesn't sound like a good way to go.

If this can be made praticle (and lord knows getting americium is damn near impossible!) it make the possability of space exploration more inviting and less risky. The time to arrive at our destinations is greatly decreased and the saftey factor goes up. Just think, a trip to the moon could turn into a "three hour tour".

Maybe CA (and the rest of us) should look at ways of conserving energy instead of "building more power plants"... lets address the 'root cause' of the energy-shortage-problem: Wastefull consumption. How much energy would be saved by halting the production of DickBlonalds Crappy Smeal toys and other useless disposable crap...

Perhaps the problem isn't the radiation source, but the detectors used.

In any case, it's probably a good idea to upgrade, especially if more features are in new smoke detectors (such as the ability to detect both smoldering and flaming fires, and perhaps a carbon monoxide detection system as well).--

I think all these stories about pie-in-the-sky technology that we won't see for decades, if ever, is entirely the wrong direction to focus attention.

I want NASA to go to Mars, not in 50 years, not in 20 years...now, or 5 years ago even better. We have the ability and to go, we have a plan(Mars direct). All we need is some vision: from our representatives in Congress and from the public.

I'm sick of waiting and I'm sick of watching NASA shoot little AIBOs at that planet and then watching them crash and burn. Spend some money, build a good, safe ship, and send some people there. But for god's sake do it now. Everyone thinks it would be hard, and they'd rather it be easy. Well guess what, it will get easy, once we do it 100 or 1000 times.

And while I have nothing against ISS, that $60 billion could have got us a round-trip ticket to Mars, instead of Mir2.

a rocket could reach Mars in only 2 weeks
Reaching Mars in 2 weeks means the rocket would have to accelerate really fast. But when it gets there its going to have to slow down to land. Is this accounted for in the speed claims?
Like in the movie Space Balls, they were traveling at "ludicrous speed". They wanted to stop but they were going to fast, they had to slow down first.

Don't believe the hype. I used to be in an M1A1 Heavy tank brigade. It is a very low level of radiation in those rounds that is only dispersed in a small amount of breathable form such as particles when the round hits something. If you were in what got hit, you're probably already dead, and if you go near something that just got hit, are you fucking insane? I've seen burning tanks after a hit -- STAY AWAY.

I know, from a reliable source, of a tank that got a non-deadly hit from a DU round (butt-shot disables, but doesn't usually kill). The geiger counter registered radiation around the hit, but nothing close to dangerous levels. You probably saw worse in your high school science classes.

Remember, it's depleted uranium. Might as well get everyone paranoid and tell them that the tank armor itself is partially made of DU.

I could go on with the technical details of DU rounds, but that would get to be a kind of long post. Tell me if you want it.

Secondly, the ISS may be the biggest boon to interplanetary space travel we've come up with so far. With it, we have the possibility of starting from outside the gravity well, which is the biggest fuel burn we have with any space travel.

The ISS is in LEO. If the earth were a peach, then the ISS would lie somewhere in the fuzz. While I'll grant that it's higher than the ground, it's not enough to make a significant difference in cost. You might think to construct spacecraft in situ to reduce costs, but then there's still the expense of transporting the raw materials and/or parts up to the ISS.

You're not going to see routine trips to Mars for 10 years at least.

I'd push the date back even farther than that. Manned colonies on Mars are still pie-in-the-sky dreaming for the most part. Zubrin, while a visionary, is like most visionaries in that his ramblings need to be taken with a grain of salt and a healthy dose of reality. "Living off the land" sounds very appealing--very "Wild West" and "Lewis and Clark." But it's also foolhardy when you realize that we simply don't know what we need to know about Mars to be able to make such a scheme work. Lewis and Clark could make canoes when they needed to cross rivers. It's doubtful that a manned mission would ever have the resources to build, say, spare fuel cells or atmosphere-transmogrification-into-rocket-fuel facilities as Zubrin envisions. Then there's the problem of cosmic ray bombardment both in the trip to Mars and in the time spent on the surface. The most recent estimates based on our best information to date puts human exposure in the 0.5 heavy nuclei/year/cell in the body range for the trip there, and something like 0.1 heavy nuclei / year while there. This doesn't sound too healthy to me. Shielding won't work very well either. Unless it is very thick (and thus, very expensive), the result will just be bombardment by showers of secondary particles, rather like ricocheting bullets inside tanks.

We have to face the fact that unmanned space exploration is all there will be in the near future. When the robots teach us enough that we can bring the risk (financial and safety) down to acceptable levels, and when we find enough impetus to go there in person, then we might consider manned missions. Not until then, I'm afraid.

Sure, we can go to Mars in a year or two with Mars Direct... but consider:

Fourty some years ago there were several methods for getting to the moon under consideration - among them were:

Assembly in Orbit -- building the infrastructure to dock sufficient resources together in earth orbit and from there go to the moon.

"Moon Direct" -- a single rocket that could deliver two people to the moon. No in-space infrastructure needed, relativly cheap and fast.

We went with Moon Direct - and sent 12 (14 if you count Apollo 13) people to the moon. Since then nothing.

Perhaps if we had gone the other way, we would have built the space station in LEO first. Used it as a staging point for missions to the moon and been left with an easy jumping off point for further missions to the moon, mars, and beyond.

I fear that if Mars Direct is the way we get to mars, you will be able to count the missions to mars on the fingers of one hand.

Mars is a much smaller planet than the Earth, it gets less than half the sunlight, and it's completely arid. Transporting the entire population of earth there would require a hell of a lot of Am-242. Then when we get there what would we do? We need to fix this planet, not move on.

Okay, so the idea is to make it to Mars in two weeks. What about going to other places in the solar system? Say, Jupiter...Europa...hmmm. We could literally send folks out there and keep sending materials to follow them. Forget about having to recycle every atom one takes to Mars, if the trip is hardly longer than a moon shot, I think we've got it covered.

Right now, the biggest problem with getting to Mars is being able to keep people alive for the 2 years (or something like that) round trip. Watch out, now we'll do it for you in six minutes! Oh, wait....

Ya know, you're right. Let's get rid of all of that nuclear powered stuff, expecially in space. After all, we don't want to spoil that wonderfull pure environment out there with filthy dirty icky radiation.

Of course, the first, and biggest source of nuclear radiation we'd have to get rid of would be the sun, and all of those other stars. Did you know that they pump out enough radiation to kill you if you go out there without shielding? We'd best hurry to get rid of them first, since they give off a whole heck of a lot more radiation, AND radioactive crud than any rocket we build could manage to do.

i was reading an article in a Scientific American from a few months back about the vasimr propulsion system. it can get up to 300km per second and seems to be very fuel efficient.
check out SciAm's comparisons [sciam.com].

Americium and Neptunium should only be used for there god-given purpose. Cool little mini-nukes!
It is a waste of our precious scientists time trying to speed travel to Mars. First we must have popcan sized mini-nukes, then we can move on to such ungainly pursuits as space exploitation.

You know, NASA and research labs and universities can be spending time and resources on developing new ways of throwing ourselves around the solar system... but it doesn't solve that nagging little problem of the annoying gravity well we call home.

I say start pouring money into new launch systems and bring down the cost of putting things into Earth orbit. Once orbital access is cheap and readily available... maybe have a moonbase or three established... then interplanetary travel research will do us a lot more good.